Identification of Green Rust Compounds in the Aqueous Corrosion Processes of Steels; the Case of Microbially Induced Corrosion and Use of 78 K CEMS

Fe(II)-Fe(III) hydroxy-sulphate Green Rust 2, GR2(SO₄ ^–), is obtained by microbially induced corrosion of steel. Transmission Mössbauer spectroscopy (TMS) was used to characterise the corrosion products of steel sheet piles under the biofilm at low sea-water level in a harbour. To understand the process, iron coupons maintained in aqueous solutions of 4 M NaCl and 0.1 M NaHCO₃ of pH 7.4 were studied by X ray diffraction and conversion electron Mössbauer spectroscopy (CEMS) at 78 K. The Fe(II)-Fe(III) hydroxy-carbonate, GR1(CO₃ ^–), covers the surface, as predicted by the E_h-pH diagram.     

Na1.72Mn3.28(AsO4)3

The single crystal of sodium manganese arsenate (1.72/3.28/12), Na_1.72Mn_3.28(AsO₄)₃, used for analysis was prepared by solid‐state reaction at 1073 K. The compound crystallizes in the monoclinic system in space group C2/c. The structure consists of a complex network of edge‐sharing MnO₆ octahedral chains, linked together by AsO₄ tetrahedra, forming two distinct channels, one containing Na⁺ cations and the other occupied statistically by Mn⁺ and Na⁺ cations.     

Influence of operating conditions on the retention of phosphate in water by nanofiltration

The objective of this study was to investigate the retention of phosphate anions, H₂PO₄⁻ and HPO₄²⁻, by nanofiltration. The first part of this study deals with the characterisation of the NF200 membrane used in permeation experiments with aqueous solutions of neutral organic and charged inorganic solutes. In the second part the effects of feed pressure, ionic strength, concentration and pH on the retention of phosphate anions were investigated. Results show that the membrane is negatively charged, its pore radius is around 0.5 nm and the retention order for the salts tested was R(Na₂SO₄) > R(NaCl) > R(CaCl₂). The retentions of phosphate anions are in the order of 85% for H₂PO₄⁻ and 96% for HPO₄²⁻. They are relatively high when compared to retentions of other anions with the same charge. The retentions of phosphate anions, particularly the monovalent species, depend on the chemical parameters (feed concentration, ionic strength, and pH) and applied pressure. The experimental data were analysed using the Speigler–Kedem model and the transport parameters, i.e., the reflection coefficient (σ) and solute permeability (P_s) have been determined.     

Cleavage of Carbon Dioxide C=O Bond Promoted by Nickel-Boron Cooperativity in a PBP-Ni Complex

The synthesis and characterization of (^tBuPBP)Ni(OAc) ( 5 ) by insertion of carbon dioxide into the Ni−C bond of (^tBuPBP)NiMe ( 1 ) is presented. An unexpected CO₂ cleavage process involving the formation of new B−O and Ni−CO bonds leads to the generation of a butterfly-structured tetra-nickel cluster (^tBuPBOP)₂Ni₄(μ-CO)₂ ( 6 ). Mechanistic investigation of this reaction indicates a reductive scission of CO₂ by O-atom transfer to the boron atom via a cooperative nickel-boron mechanism. The CO₂ activation reaction produces a three-coordinate (^tBuP₂BO)Ni-acyl intermediate ( A ) that leads to a (^tBuP₂BO)−Ni^I complex ( B ) via a likely radical pathway. The Ni^I species is trapped by treatment with the radical trap (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) to give (^tBuP₂BO)Ni^II(η²-TEMPO) ( 7 ). Additionally, ¹³C and ¹H NMR spectroscopy analysis using ¹³C-enriched CO₂ provides information about the species involved in the CO₂ activation process.     

1,3-Diborata-2,4-diphosphoniocyclobutane-1,3-diyls communicate through a para-phenylene linker

The presence of a second 1,3-diborata-2,4-diphosphoniocyclobutane-1,3-diyl in the para-position of a phenylene linker favors the diradical form over the 1,3-diborata-2,4-diphosphoniobicyclo[1.1.0]butane bond stretch isomer, as long as the two planar diradical units are coplanar with the linker. This demonstrates that two BPBP diradicals communicate through the phenyl ring.     

Effect of instant controlled pressure drop treatments on the oligosaccharides extractability and microstructure of Tephrosia purpurea seeds

The study of the oligosaccharides extracted from Tephrosia purpurea seeds was undertaken using the instant controlled pressure drop (DIC) as a pre-treatment prior to conventional solvent extraction. This DIC procedure provided structural modification in terms of expansion, higher porosity and improvement of specific surface area; diffusion of solvent inside such seeds and availability of oligosaccharides increase notably. In this paper, we investigated and quantified the impact of the different DIC operative parameters on the yields of ciceritol and stachyose extracted from T. purpurea seeds. The treatment could be optimized with a steam pressure (P) (P=0.2 MPa), initial water content (W) (W=30% dry basis (DB)) and thermal treatment time (t) (t=30s). By applying DIC treatment in these conditions, the classic process of extraction was intensified in both aspects of yields (145% of ciceritol and 185% of stachyose), and kinetics (1h of extraction time instead of 4h for conventional process). The scanning electron microscopy micrographs provided evident modifications of structure of seeds due to the DIC treatment.     

Aurophilic self-assembly of a Mo4Au2 phosphinidene complex with an unprecedented H-shaped planar metal core

The isomers [Mo2Cp2(mu-kappa(1):kappa(1),eta(6)-PR*)(CO)2] (1) and [Mo2Cp(mu-kappa(1):kappa(1),eta(5)-PC5H4)(CO)2(eta(6)-HR*)] (2) (Cp = eta(5)-C5H5; R* = 2,4,6-C6H2(t)Bu3) react with [AuCl(THT)] and with the cation [Au(THT)2](+) (THT = tetrahydrothiophene) to give phosphinidene-bridged Mo2Au complexes resulting from the addition of an AuCl or Au(THT)(+) electrophile to their multiple P-Mo bonds. Removal of the Cl(-) or THT ligand from these derivatives causes a dimerization of the trinuclear structures to give the cationic derivative [{AuMo2Cp(mu3-kappa(1):kappa(1):kappa(1),eta(5)-PC5H4)(CO)2(eta(6)-HR*)}2](2+), which displays a novel H-shaped metal core held by strong Mo-Au dative bonds [2.768(1) A] and an aurophilic interaction [Au-Au = 3.022(1) A].